The present invention relates to a method for the A/D conversion of analog signals by means of an A/D converter and to a corresponding A/D converter arrangement.
In complex applications, different analog input signals have to be fed to an A/D converter and converted. An A/D conversion of the individual input signals may be requested in this case by different request sources, with the request sources generating request signals each time in order in this way to request the A/D conversion of a given signal channel at the A/D converter.
FIG. 2 is a simplified block circuit diagram of a known A/D converter arrangement, with an A/D converter 6 being controlled by an analog multiplexer 3. The multiplexer 3 is used to select a plurality of analog signals which are each assigned to different signal channels 2. Also provided is a control unit 8 which, as a function of the control information fed to it, controls the multiplexer 3 in such a way that a given signal channel 2 is selected and the corresponding analog signal is fed to A/D converter 6 for A/D conversion. After the conversion of a sampled value of this analog signal, the result of the A/D conversion is stored in a result register 7. Hence it is also possible in this way for the control unit 8 to specify the mode of operation of the A/D converter arrangement to enable not only a single-channel conversion to be performed but also an autoscan conversion where all the signal channels 2 are converted once and one after the other, etc.
In conventional A/D converter arrangements, basic settings are provided for the A/D converter 6 which may relate to, for example, the resolution, the sampling time or else the interrupt generation for the conversion requested. These basic settings are preset in fixed form by means of the internal architecture of the A/D converter 6 or the A/D converter arrangement. A change to these basic settings by software means for example is not possible and it is therefore equally impossible for the properties of the A/D converter 6 to be adapted to the particular application, as a result of which the scope of application of the entire A/D converter arrangement is limited.
The object on which the present invention is based is therefore to propose a method for the A/D conversion of analog signals and a corresponding A/D converter arrangement whereby these limitations can be overcome and greater flexibility achieved.
This object is achieved in accordance with the present invention by a method having the features given in claim 1 and by an A/D converter arrangement having the features given in claim 19. The subclaims in each case describe preferred embodiments of the present invention.
It is proposed in accordance with the invention for certain settings or operating parameters of the A/D converter arrangement to be set as a function of the signal channel to be converted at the time. The operating parameters able to be set in a channel-specific way may in particular be parameters of the A/D converter, thus enabling the resolution, the sampling time, the conversion time, the calibration time or the range of measurement for example of the A/D converter to be individually set for each signal channel. This enables the processing of the individual signals channels to be adapted to the environment in the best possible way and the overall behaviour of the A/D converter arrangement to be optimised.
The setting of the A/D converter can be effected both by software means, i.e. by a suitable program, and by hardware means.
Each signal channel may have its own channel-specific settings assigned to it, which become active and are used for setting the A/D converter whenever an analog signal from the signal channel concerned is to be converted. To reduce the volume of data to be managed, the channels may also be combined into groups, in which case all the channels in a group are processed with the same settings. Where there are a plurality of request or triggering sources present which each generate request signals for A/D conversions, these sources too may have different settings assigned to them, as a result of which all the channels for whose signals an A/D conversion is requested by the same request source are processed with the same settings. Optimum flexibility can be achieved in particular when the principles described above of assigning the different settings are combined with one another. It may for example be extremely advantageous for a channel to be operated with its channel-specific settings unless a certain request source having its own settings requests the A/D conversion of this channel. The settings specific to the request source are thus given priority over the channel-specific settings when the settings are being selected.
As well as the parameters described above of the A/D converter it is also possible for other operating parameters of the A/D converter arrangement, which relate for example to certain digital functions of the A/D converter arrangement which form reactions to an A/D conversion, to be set, by which means it is possible to obtain a reduction in the load on the CPU. It is for example possible for certain parameters of interrupt generation, limit-value detection or short-circuit or line-break detection to be set or activated in a channel-specific way.